Field of the Invention
The present invention relates to a motor control device provided with power failure management in AC power supply failure at the time of driving a motor.
Description of the Related Art
Conventionally, as disclosed in Japanese Laid-open Patent Publication No. 2011-101474, Japanese Laid-open Patent Publication No. 2011-209936, Japanese Patent No. 3,472,433, and Japanese Patent No. 3,616,759, for instance, there is proposed a motor control device provided with a power failure detection unit configured to detect AC power supply failure at the time of driving a motor and to generate a power failure detection signal in accordance with detection of power failure, and a control unit configured to control the motor for stopping the motor in response to detection of power failure, as a motor control device provided with power failure management in AC power supply failure at the time of driving a motor. In this configuration, internal wiring is disposed between the output line of AC power supply and the power failure detection unit.
Further, as disclosed in Japanese Laid-open Patent Publication No. Hei 10-271866, Japanese Patent No. 3,369,346, and Japanese Patent No. 4,154,679, for instance, there is proposed a motor control device provided with a power failure detection unit configured to detect AC power supply failure at the time of driving a motor and to generate a power failure detection signal in accordance with detection of power failure, and a control unit configured to control the motor for retracting a driven body driven by the motor in response to detection of power failure, as a motor control device provided with power failure management in AC power supply failure at the time of driving a motor. In this configuration, internal wiring is disposed between the output line of AC power supply and the power failure detection unit, as well as the above configuration.
Furthermore, as disclosed in Japanese Patent No. 3,541,121, for instance, there is proposed a motor control device provided with a power failure detection unit configured to detect AC power supply failure at the time of driving a motor and to generate a power failure detection signal in accordance with detection of power failure, and an electric power supply unit configured to supply electric power to a DC link unit configured to accumulate electric power for driving the motor in response to detection of power failure, as a motor control device provided with power failure management in AC power supply failure at the time of driving a motor. In this configuration, internal wiring is disposed between the output line of AC power supply and the power failure detection unit, as well as the above configuration.
When a plurality of motors are controlled in order to stop a motor or an retract a driven body driven by the motor in AC power supply failure at the time of driving the motor, a plurality of DC-AC converter devices corresponding to the respective motors are individually configured. Therefore, it would be necessary to provide a power failure detection unit and a control unit for each of the DC-AC converter devices, in other words, to use power failure detection units and control units respectively corresponding to DC-AC converter devices.
The power failure detection timings by power failure detection units may differ from each other by variation of components constituting each of the power failure detection units. Further, the power failure detection timings by power failure detection units may differ from each other by an influence of voltage drop in internal wiring disposed between the output line of AC power supply and a power failure detection unit. Furthermore, the power failure detection timings by power failure detection units may differ from each other by a difference in instantaneous power failure tolerance amount of a device, in which each of the power failure detection units is installed.
Therefore, control for power failure management in AC power supply failure at the time of driving a motor may be complicated in order to avoid adverse effects due to different power failure detection timings by power failure detection units on motor control.
Further, when electric power is supplied to a DC link unit, in addition to motor control for stop a motor or retracting a driven body driven by the motor in AC power supply failure at the time of driving the motor, it would be necessary to use both a power failure detection unit with respect to a control unit and a power failure detection unit with respect to an electric power supply unit.
The power failure detection timing by a power failure detection unit with respect to a control unit may differ from the power failure detection timing by a power failure detection unit with respect to an electric power supply unit due to variation of components constituting each of the power failure detection units. Further, the power failure detection timing by a power failure detection unit with respect to a control unit may differ from the power failure detection timing by a power failure detection unit with respect to an electric power supply unit due to a difference in instantaneous power failure tolerance amount of a device, in which each of the power failure detection units is installed.
Adverse effects due to a difference between the power failure detection timing by a power failure detection unit with respect to a control unit and the power failure detection timing by a power failure detection unit with respect to an electric power supply unit may affect the motor control. For instance, although power failure is detected by a power failure detection unit with respect to a control unit, power failure may not be detected by a power failure detection unit with respect to an electric power supply unit. In this case, it is impossible to stop a motor or retract a driven body driven by the motor in AC power supply failure at the time of driving the motor.
As described above, control for power failure management in AC power supply failure at the time of driving a motor may be complicated in order to avoid adverse effects due to a difference between the power failure detection timing by a power failure detection unit with respect to a control unit and the power failure detection timing by a power failure detection unit with respect to an electric power supply unit on motor control. The aforementioned control may be further complicated, as the number of devices equipped with a power failure detection unit increases. This makes it difficult to extend a device such as a power failure management device.